The endoplasmic reticulum (ER) stress response (ERSR) is one of the major defense mechanisms that protect against cellular insult but if unchecked leads to apoptotic cell death. The ERSR has three arms initiated by PERK, IRE1, ATF6, respectively. Preliminary data show the acute activation of all three ERSR signaling pathways in endothelial cells (ECs) after SCI. Most importantly, we show that attenuation of PERK signaling in CHOP-/- (the downstream effector of PERK) mice or after i.v. salubrinal (which sustains protein synthesis inhibition) leads to enhanced functional recovery after SCI in WT mice. We found an acute vasoconstrictive phase following SCI and can enhance EC protection by the vasodilator nimodipine plus the vasoprotector glibenclamide in WT mice. Specifically, Aim 1 will delineate the specific effectors that underlie ERSR-mediated EC death by PERK signaling. We will determine if reducing PERK or ATF4 signaling in ECs after SCI will enhance functional recovery after SCI. This will be done using available transgenic mice (Aim 1a) and siRNA methods (Aim 1b). We hypothesize that the earlier in the ERSR pathway that inhibition occurs, the more extensive the vasoprotection and recovery. Aim 2 will characterize the acute activation profile of the ERSR in FACS purified ECs when one signaling pathway is deleted (Aim 2a), their effects on spinal cord microvasculature (Aim 2b) and the functional consequences (Aim 2c). Aim 3 will test whether EC rescue by ER stress inhibitors can be improved when combined with the vasodilators, nimodipine or MgSO4, the mainstay treatments for CNS vasospasm. Aim 3a will optimize vasodilation protocols. Aim 3b will optimize treatment regimens for salubrinal and two chemical chaperones that influence ERSR signaling: TUDCA (in clinical trials for ALS) and PBA (FDA-approved). We will then test whether optimized vasodilation would further improve the efficacy of those drugs using both pharmacological and genetic approaches. Aim 3c will define determine the therapeutic window. Collectively, the experiments outlined in these 3 Aims delineate a strategy to optimally inhibit ER stress in ECs to maximize functional recovery after SCI and determine whether this approach is clinically relevant.